Drag over the grimy panel to sweep the jet. Grime only clears where impact pressure exceeds the adhesion threshold.
Pressure washing is fundamentally a threshold process: a jet's impact pressure at the surface either exceeds a grime layer's adhesion strength, in which case it clears quickly, or it doesn't, in which case nothing happens no matter how long you hold the jet there. This simulation lets you sweep a jet across a grimy panel by hand and see exactly where that threshold is crossed, while a live chart shows how impact pressure falls off as you back the nozzle away from the surface.
A grimy panel you sweep a jet across by dragging, plus a live impact-pressure-vs-standoff-distance chart with the current adhesion threshold and jet position both marked.
Set Pump Pressure, Standoff Distance and Grime Adhesion Strength, then click and drag across the panel to sweep the jet. Grime only clears where impact pressure exceeds the adhesion threshold — watch the removal margin readout to see by how much.
Because impact pressure falls off with the square of standoff distance in this model, doubling your distance from the surface cuts effective cleaning pressure roughly to a quarter — which is exactly why cleaning guides for pressure washers emphasise working close to (but not directly on) delicate surfaces.
A pressure-washer jet is coherent only for a short distance before it spreads and loses core pressure; this simulation models that spreading with a simple 1/(1+(d/d0)²) falloff, capturing why moving the nozzle even a little further from the surface can drop effective cleaning pressure sharply.
Surface-cleaning engineering treats adhesive removal as a yield-type process: below a critical impact pressure, the grime layer simply doesn't detach no matter how long the jet dwells there, while above it, removal proceeds quickly — this simulation reproduces that all-or-nothing character rather than a gradual erosion curve.
Only once it's high enough to push the local impact pressure above the adhesion threshold at your chosen standoff distance — below that threshold, additional pump pressure alone won't help if the standoff distance is too large for it to reach the surface effectively.
It's the impact pressure at the jet's core minus the current adhesion-strength threshold. A positive margin means grime clears at that spot; a negative margin means the jet has no effect there regardless of dwell time.